Six-figure bonuses scattered like shrapnel among lucky staff. No, not the trading floor on the 15th storey of some gleaming tower in Canary Wharf, but the shop floors of Sports Direct, the purveyors of cut-price trainers. Over 2,000 staff – working everywhere from stockrooms to cash tills – will enjoy a once-in-a-lifetime jackpot. Highly unusual; and yet research indicates that it is those in relatively routine occupations who should get bonuses – not the City's securitisation experts. Take a study for a branch of the US central bank, in which behavioural economists offered students cash to tap a keyboard as fast as they could, and also to add up numbers. The bonuses helped undergraduates tap those keys fast; but when it came to the arithmetic, the dollars made performance worse. "Tasks that involve only effort are likely to benefit from increased incentives," the economists concluded. "While for tasks that include a cognitive component, there seems to be a level of incentive beyond which further increases can have detrimental effects on performance." What such research indicates is that bonuses can spur on workers to do basic tasks, such as scanning in a pair of Speedos. They don't help that credit-derivatives saleswoman do her work to a higher standard. She may not agree, but as Upton Sinclair remarked: "It is difficult to get a man to understand something when his salary depends upon his not understanding it." And his words weren't inspired by a stock-option plan.